Summary for clan SH

Summary Alignment Structure Literature
Clan type peptidaseS21.002 - cytomegalovirus assemblin (human herpesvirus 5), MEROPS Accession MER0000613 (peptidase unit: 1-256); PDB accession 1LAY
HistoryPEPTIDAS.TXT (SwissProt document)
DescriptionSerine nucleophile; catalytic residues in the order His, Ser, His in sequence
Contents of clanClan SH contains only family S21 .
EvidenceAll known members of the clan are endopeptidases from DNA viruses and are involved in the assembly of the viral prohead (Rawlings & Barrett, 2004).
Catalytic mechanismThe order of the catalytic triad is His, Ser, His.
Peptidase activityFamily S21 contains assemblin. Assemblin is involved in the late stages of virion assembly, and breaks down the scaffold protein upon which the viral prohead is assembled (Rawlings & Barrett, 2004).
Protein foldTertiary structures have been determined for several members of the clan. The first structure determined was for assemblin from human cytomegalovirus (S21.002; Chen et al., 1996). Peptidases in clan SH are alpha/beta proteins containing a beta barrel surrounded by helices. The active site residues are within the barrel.
Homologous non-peptidase familiesThe fold is unique to clan SH.
Activation mechanism(See family S21.)
Other databases SCOP50789

Families

Family Family Type Peptidase Structure
S21 cytomegalovirus assemblin (human herpesvirus 5) Yes
S73 gpO peptidase (Enterobacteria phage P2) (Enterobacteria phage P2) -
S77 prohead peptidase gp21 (bacteriophage T4) (Enterobacteria phage T4) -
S78 prohead peptidase (bacteriophage HK97) (Enterobacteria phage HK97) -
S80 prohead peptidase gp175 (Pseudomonas aeruginosa phage phiKZ) (Pseudomonas phage phiKZ) -

Distribution of clan SH among Kingdoms of Organisms

FamilyBacteriaArchaeaProtozoaFungiPlantsAnimalsViruses
S21------+
S73+---+++
S77----+++
S78+++-+-+
S80------+
Clan+++-+++